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[CHIA-3793] after the hard fork, disallow block references #20218

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[CHIA-3793] after the hard fork, disallow block references #20218

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fd84364
after the hard fork, disallow block references
arvidn Nov 3, 2025
9d735e9
disable hard-fork 2 tests until we have a new test cache
arvidn Nov 4, 2025
f4a0b5e
fix rate limits test
arvidn Nov 4, 2025
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6 changes: 5 additions & 1 deletion chia/consensus/block_body_validation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -341,10 +341,14 @@ async def validate_block_body(
# the generator ref list for this block (or 'one' bytes [0x01] if no generator)
# 8b. The generator ref list length must be less than or equal to MAX_GENERATOR_REF_LIST_SIZE entries
# 8c. The generator ref list must not point to a height >= this block's height
if block.transactions_generator_ref_list in (None, []):
if block.transactions_generator_ref_list == []:
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@richardkiss richardkiss Nov 5, 2025

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Is this just a tidy-up, or is it required?

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@arvidn arvidn Nov 5, 2025 •
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correct, this is unrelated. I was a bit surprised mypy didn't flag this. transaction_generator_ref_list is not Optional[]. It can't be None.

if block.transactions_info.generator_refs_root != bytes([1] * 32):
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@richardkiss richardkiss Nov 5, 2025

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This is such a bizarre magic number. I'm very puzzled why we wouldn't just use the serialization for the empty list. But I don't suppose it much matters now.

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@arvidn arvidn Nov 5, 2025 •
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this isn't a list, it's a bytes32. it must always be 32 bytes in the serialization. Still, It could be a named constant.

return Err.INVALID_TRANSACTIONS_GENERATOR_REFS_ROOT
else:
# With hard fork 2 we ban transactions_generator_ref_list.
if prev_transaction_block_height >= constants.HARD_FORK2_HEIGHT:
return Err.TOO_MANY_GENERATOR_REFS

# If we have a generator reference list, we must have a generator
if block.transactions_generator is None:
return Err.INVALID_TRANSACTIONS_GENERATOR_REFS_ROOT
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13 changes: 9 additions & 4 deletions chia/consensus/blockchain.py
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Expand Up @@ -33,6 +33,7 @@
from chia.consensus.find_fork_point import lookup_fork_chain
from chia.consensus.full_block_to_block_record import block_to_block_record
from chia.consensus.generator_tools import get_block_header
from chia.consensus.get_block_challenge import prev_tx_block
from chia.consensus.get_block_generator import get_block_generator
from chia.consensus.multiprocess_validation import PreValidationResult
from chia.full_node.block_store import BlockStore
Expand Down Expand Up @@ -698,12 +699,16 @@ async def validate_unfinished_block_header(
if len(block.transactions_generator_ref_list) > self.constants.MAX_GENERATOR_REF_LIST_SIZE:
return None, Err.TOO_MANY_GENERATOR_REFS

if (
self.try_block_record(block.prev_header_hash) is None
and block.prev_header_hash != self.constants.GENESIS_CHALLENGE
):
prev_b = self.try_block_record(block.prev_header_hash)
if prev_b is None and block.prev_header_hash != self.constants.GENESIS_CHALLENGE:
return None, Err.INVALID_PREV_BLOCK_HASH

prev_tx_height = prev_tx_block(self, prev_b)

# With hard fork 2 we ban transactions_generator_ref_list.
if prev_tx_height >= self.constants.HARD_FORK2_HEIGHT and block.transactions_generator_ref_list != []:
return None, Err.TOO_MANY_GENERATOR_REFS
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@richardkiss richardkiss Nov 5, 2025

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I'm a bit puzzled as to why this is checked in multiple places. Maybe one is for all blocks and another is just for "transaction blocks"?

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@arvidn arvidn Nov 5, 2025

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We check it in BlockTools, to make sure no test is trying to create an invalid block.
We check it in block body validation, which is the main block validation function.
We also check it when validating unfinished blocks, which is a bit trickier because the height of the block isn't as well known.


if block.transactions_info is not None:
if block.transactions_generator is not None:
if std_hash(bytes(block.transactions_generator)) != block.transactions_info.generator_root:
Expand Down
4 changes: 4 additions & 0 deletions chia/simulator/block_tools.py
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Expand Up @@ -385,6 +385,10 @@ def setup_new_gen(
transaction_data: Optional[SpendBundle],
block_refs: list[uint32],
) -> Optional[NewBlockGenerator]:
if prev_tx_height >= self.constants.HARD_FORK2_HEIGHT:
assert block_refs == [], "block references are not allowed after hard fork 2"
dummy_block_references = False

# we don't know if the new block will be a transaction
# block or not, so even though we prepare a block
# generator, we can't update our state (like,
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